In a future communications system of the 3rd Generation Partnership Project (3GPP), a network may be divided into a plurality of logical network slice instances of a core network on a set of physical devices of the core network using a slicing technology. Each network slice instance of the core network may be customized based on a specific commercial scenario or a specific user requirement, to ensure isolation between network slice instances while satisfying diversified services. An operator can satisfy a specific requirement of each service by freely and flexibly combining network performance indicators such as a rate, a capacity, coverage, a delay, reliability, security, and availability.
Generally, the network slice instance of the core network is briefly referred to as a network slice. Introduction of the network slice puts forwards a new requirement on a selection policy on a terminal side. The network includes the plurality of customized network slice instances of the core network, each slice instance may serve a particular user group, and some complex terminals further have a capability and a requirement of simultaneously accessing a plurality of network slice instances. Therefore, the terminal needs to know a correspondence between an application (App) of the terminal and a slice type.
For example, when an application of a terminal requests a service, the terminal needs to know a type of a network slice that the application needs to access, and provide corresponding assistance information to assist network slice selection and user plane session establishment. In addition, when a plurality of protocol data unit (PDU) sessions currently have been established on a terminal side, and a new application on the terminal side requests a service, the terminal needs to determine whether a currently established PDU session can satisfy a service request of the new application. If all currently existing PDU sessions cannot satisfy the service request of the new application, the terminal further initiates a new user plane session request for the new application. For example, a PDU session of an enhanced mobile broadband (eMBB) type currently has been established on the terminal side. A new application on the terminal side needs to send service data. If the application also requires the PDU session of the eMBB type, the terminal side may directly send the service data of the application using the currently established PDU session of the eMBB type. However, if the application requires a PDU session of an Internet of Things (IoT) type, the terminal needs to initiate a new PDU session establishment request, to establish the PDU session of the IoT type.
In an existing solution of a 3GPP standard, a terminal device is, for example, user equipment (UE), and a preconfigured network slice selection policy (NSSP) is stored on a UE side. The NSSP may be configured by an operator for the UE, for example, stored in a subscriber identity module card (SIM), or may be preconfigured when the terminal device is delivered from a factory, or may be configured on the UE when an application is installed.
The NSSP includes a mapping relationship between an application and a service/slice type (SST). When an application is started, the UE maps the application to an SST using the NSSP. If a currently existing PDU session can support the SST, the UE sends a data stream of the application using the PDU session. If no PDU session currently can support the SST, the UE initiates a new PDU session establishment request that carries the SST.
The foregoing solution has a problem: The configured SST on the UE side changes and is updated by a network side in an actual process. In an access procedure discussed in an existing 3GPP standard, the UE provides a configured SST in an Attach message. After accepting access by the UE, the network side returns an Accepted SST to the UE in an Attach Accept message. The configured SST is not completely consistent with the accepted SST in many scenarios. As a result, the UE initiates a PDU session establishment request, causing network resource waste.